The cross-referenced application, now U.S. Pat. No. 5,430,515, discloses a cassette retaining apparatus comprising a holding chamber into which a film cassette is to be inserted and from which the cassette may be removed, and retaining means biased into engagement with the film cassette to retain the cassette in the chamber. The retaining means includes a retaining piece supported for translation into and out of a closed-end groove in the cassette to engage and release the cassette, and a helical compression spring which continuously urges the retaining piece to be translated into the groove to engage the cassette. When the cassette is inserted into the chamber, the cassette first depresses the retaining piece out of its way contrary to the urging of the spring. However, as the groove is positioned opposite the retaining piece, the spring then urges the retaining piece to drop into the groove. When the cassette is removed from the chamber, the cassette depresses the retaining piece contrary to the urging of the spring to eject the retaining piece from the groove to disengage the cassette. Thus, the spring provides only one force to bias the retaining piece into engagement with the cassette, which force equally resists insertion of the cassette in the chamber and removal of the cassette from the chamber. It is good for the force to be relatively strong to urge the retaining piece into the groove to make it difficult for the cassette to be unintentionally dislodged from the chamber. However, it is a drawback that the force makes it equally difficult for the cassette to depress the retaining piece out of its way during insertion of the cassette into the chamber.